A. Field of Invention
The present invention relates in various aspects to extruded concrete articles made from a mixture of water, aggregate and binder. According to the process, the binder hydrates in the presence of the water to form a high-strength concrete article, such as bricks. In another aspect, the invention relates to processes and apparatus for making the concrete articles.
B. Background Art
Various efforts have been made to make extruded concrete articles. But the present inventor is not aware of any successful procedures that have been implemented commercially to provide low cost building materials having properties comparable to conventional "molded" concrete. Accordingly, the present invention is believed to satisfy a long-felt need. It is contemplated that one of the problems with other processes lies in the inability to reliably make articles that meet the specifications of conventional molded concrete. Certain aspects relating to the use of vacuum to make extruded concrete articles have been published. For example, Anderson et al., U.S. Pat. No. 5,549,859, discusses a vacuum-type chamber for making concrete articles. However, these and other processes and devices have various shortcomings, and fail to disclose or suggest the present invention, which includes improved methods and apparatus for making extruded concrete articles.